This invention relates to an electromagnetic shielding structure used at a portion where electric wires (cables) are connected respectively to input/output terminals of a motor of an electric car or an ordinary electronic equipment.
In the case of connecting wires (cables) to input/output terminals, for example, of a motor mounted on an electric car, there is used a grounding structure in which a shielding member is connected to amounting member (such as a casing of the motor) for grounding purposes, in order to prevent electromagnetic waves from leaking from the wires (cables) to the exterior and also to protect the wires (cables) against the influence of electromagnetic waves from the exterior.
One such related electromagnetic shielding structure is disclosed in JP-A-10-241792, and is shown in FIG. 9. Specifically, an electrically-conductive connector body 2 is fixedly secured by bolts 5 to a mounting member 1 connected to the ground G. A pressing spring (resilient member) 4 is mounted between the connector body 2 and a connector retaining member 3. Wires 6 are connected to this connector structures and this connector structure is mounted on the mounting member
The wires 6 are covered with an electrically-conductive sheet 7 over their entire length, and are connected respectively to input/output terminals of an equipment via respective metal terminals 8 each press-fastened to an end portion of the corresponding wire. In this case, an end portion of the electrically-conductive sheet 7 is exposed, and this exposed end portion is compressively held between the connector body 2 and the connector retaining member 3 by a resilient force of the pressing spring 4. In this manner, the electrically-conductive sheet 7 is connected to the mounting member 1, connected to the ground G, thereby achieving the electromagnetic shielding conduction.
The electromagnetic shielding structure as shown in FIG. 9, disclosed in the above publication, has the following problem. Namely, the electrically-conductive sheet 7 is pressed into contact with the connector body 2 by the resilient force of the pressing spring 4, and by doing so, the two are connected together. However, any waterproof and rust-proof measures are not provided at this connection portion. When moisture penetrates into the connection portion and when this structure is used for a long period of time in an environment in which the temperature changes, rust develops on the contact surface of the connection portion. The pressing load due to the contact pressure, produced by the pressing spring 4, is limited, and when such rust develops a stable contact resistance of the electrically-conductive sheet 7 relative to the connector body 2 can not be obtained, and therefore the effective electromagnetic shielding effect can not be expected.
It is therefore an object of this invention to provide an electromagnetic shielding structure capable of achieving the effective electromagnetic shielding by enhancing the reliability of the connection.
In order to solve the aforesaid object, the invention is characterized by having the following arrangement.
(1) An electromagnetic shielding structure comprising:
a shielding block which is electrically and sealingly connected to a mounting member, connected to a ground, and includes an annular groove formed in an outer peripheral of the shielding block over an entire periphery thereof;
an elastic seal member which is sealingly fitted and held in the shielding block that a wire is passed through the elastic seal member in intimately contacted relation thereto;
a flexibility and electrical conductivity shielding sheet covering the wire over entire length thereof; and
a retaining band engageable with the annular groove for tightly fastening the shielding sheet on the annular groove.
(2) The electromagnetic shielding structure according to (1), wherein the shielding block is an electrically-conductive, tubular housing which is connected to the mounting member, and holds the elastic seal member.
(3) The electromagnetic shielding structure according to (2), wherein the elastic seal member is passed through the mounting member in intimately contacted relation thereto, and is abutted against a rear end of a metal terminal press-fastened to an end portion of the wire.
(4) The electromagnetic shielding structure according to (1), wherein the shielding block is an electrically-conductive lid member which is connected to the mounting member such that the wire is passed through the lid member to be prevented from shaking, and the lid member holds the elastic seal member, and seals the elastic seal member from the exterior.
(5) The electromagnetic shielding structure according to (1), wherein the shielding block includes a plurality of holes for receiving a plurality of the elastic seal members, respectively.
(6) The electromagnetic shielding structure according to (5), wherein a plurality of the wires are passed through the plurality of elastic seal members, respectively.
(7) The electromagnetic shielding structure according to (6), wherein the shielding sheet covers the plurality of wires.
(8) The electromagnetic shielding structure according to (1), wherein opposite ends of the retaining band is fastened by a bolt.
(9) The electromagnetic shielding structure according to (8), wherein the shielding block includes a bolt fastening rib interposed between the opposite ends of the retaining band when the retaining band is fastened on the annular groove.
In the above structure, particularly in the case where the shielding sheet, covering the wire over the entire length thereof, is a braid, a distal end portion of the braid is connected to the mounting member connected to the ground, so as to achieve the electromagnetic shielding conduction. At this time, the distal end portion of the braid is tightly fastened and fixed to the annular groove portion in the electrically-conductive shielding block by the braid retaining band wound on the outer surface of this distal end portion. Therefore, the distal end portion of the braid can be positively and firmly connected to the mounting member. As a result, the effective electromagnetic shielding effect can be expected, and the stable electrical characteristics can be obtained, so that the reliability of the connection can be enhanced.
In the above structure, the shielding-block comprises the housing holding the elastic seal member, and the housing is electrically connected to the mounting member. Therefore, the connection to the ground is achieved.
In the above structure, the elastic seal member is extended into a longer size, and is abutted against the rear end of the metal terminal press-fastened to the end portion of the wire. Therefore, the metal terminal is prevented from rearward movement and withdrawal.
In the above structure, the shielding block comprises the lid member which holds the elastic seal member in a sealed condition, and this lid member is electrically connected to the mounting member. Therefore, the connection to the ground is achieved.